Generate a random rock or mineral from 59 real specimens. Filter by class -- igneous, sedimentary, metamorphic, or mineral -- for geology study or worldbuilding.
A rock is a naturally occurring solid aggregate of one or more minerals, which is what separates it from a mineral -- a single substance with a fixed chemical composition and crystal structure. All rocks fall into three families by how they formed: igneous from cooled magma, sedimentary from compacted particles or precipitated chemicals, and metamorphic from existing rock reworked by heat and pressure without melting. The rock cycle moves material continuously between the three, so any given atom has probably occupied all of them. Texture usually tells the story faster than composition: coarse crystals mean slow cooling underground, fine ones mean a fast chill at the surface.
This generator draws from a curated list of 59 rocks and minerals across four categories -- Igneous, Sedimentary, Metamorphic, and Mineral -- from granite and limestone to opal and obsidian, each with a description of how it forms and where it turns up.
Every result here is drawn using crypto.getRandomValues() -- the Web Crypto API's cryptographically secure randomness -- instead of Math.random(), so it's genuinely unpredictable, not just statistically random. Learn more.
Earth science students use it to drill the rock cycle's three families and their tell-tale features. Teachers use it for specimen-of-the-day prompts, collectors use it to pick what to hunt next, and worldbuilders use it to ground fictional geology in the real thing.
Generate draws one rock or mineral at random using the site's cryptographically secure randomness, guaranteed not to repeat whatever result is currently showing in single-result mode. Each single result describes the formation story and identifying traits, and the Category filter narrows the pool.
A sample of what this generator can draw, spread evenly across the full list:
A mineral is a single crystalline compound -- quartz, calcite, pyrite -- while a rock is an aggregate of minerals. The Mineral category keeps the pure species separate from the composites.
Igneous rocks freeze from molten material, sedimentary rocks build up in layers from debris and chemistry, and metamorphic rocks are either of those transformed by heat and pressure -- the whole rock cycle in three filters.
Yes -- gem minerals like opal, garnet, and topaz appear in the Mineral category with the geology behind the sparkle.
Gemstone · Periodic Element · Fossil · Geologic Period